a. Field of the Invention
This invention relates to a method for the nitration of benzene by the use of nitrogen dioxide.
B. Description of the Prior Art
In the method of producing nitro compounds, organic compound to which nitro radical being introduced reacts with a nitration reagent or reactant.
The nitration reagent is any one selected from the group of nitric acid (concentrated or diluted), mixed acid (a mixed solution of concentrated nitric acid and concentrated sulfuric acid, a mixed solution of concentrated nitric acid and fuming sulfuric acid, or mixed solution of concentrated nitric acid and acetic anhydride), anhydrous nitric acid N.sub.2 O.sub.5, organic nitrates (acetyl or benzoyl), inorganic nitrates (mainly, alkali metal salts) and sulfuric acid, or nitryltetrafluoroborate NO.sub.2.sup.+ BF.sub.4.sup.- and so forth.
Each nitration reagent is selected suitably depending on the easiness or difficulty of the reaction. The most conventional reagent is nitric acid or a mixed acid in particular, a mixed solution of concentrated nitric acid and concentrated sulfuric acid or fuming sulfuric acid.
In this method, very large amounts of nitric and sulfuric acid are used to the organic starting material so that the mother liquor i.e. the waste acid necessarily remains in fairly large quantities.
The waste acid is separated from resulted nitro compounds, and followed by heating for separation of nitric acid and concentration of sulfuric acid. Furthermore, each acid is concentrated, if desired, for the recovery. This process is commonly known as the waste acid treatment. It is preferable to utilize the waste acid, for example, for decomposing rock phosphate or super phosphate of lime in the fertilizer manufacture, but when there is no utility, the facilities are necessary for the waste acid treatment such as acid reservoirs, pipe line system and pumps for delivering acid and heat furnace for concentration of waste acid and so on. Water pollutions have been caused by the waste acid from the factories depending upon whether or not the arrangement, capacity or maintenance of those facilities are perfect.
Therefore, there is an absolute need for completing the waste acid facility as well as all waste water treatment in the department of nitration process.
No equipment or facility of waste acid treatment is operated economically because of damage i.e. corrosion or errosion thereof and much consumption of fuels. In other words, in view of the waste acid and the additional waste water treatment facilities, the cost of utilities might be negligible.
There have been known various methods for producing nitrobenzene. Those are such as a batch or continuous nitration method of using a mixed solution of nitric and sulfuric acid, azeotropic nitration method (refer to C.A. vol. 84. 1976. 135280w, and Encyclopaedia of Chemical Technology edited by Kirk-Othmer Vol. 9 page 318), and a method of nitration of benzene by the use of a solution of liquid nitrogen dioxide N.sub.2 O.sub.4 in sulfuric acid (refer to B.67 1363 [1934]) and so forth. In the above method except azeotropic nitration method, it is necessary to perform the waste acid treatment.
The method of nitration of aromatic hydrocarbon by the use of nitrogendioxide or liquid nitrogendioxide N.sub.2 O.sub.4 had been researched already at the end of the 19th century to the beginning of the 20th century, however, there has been no suitable or valid method of producing nitrobenzene in connection with these methods.
(1) Wieland reported that benzene was allowed to warm with N.sub.2 O.sub.4 in a sealed tube, resulting in the formation of trinitrobenzene, oxalic acid and carbondioxide. (refer to B. 67 1362 [1934])
(2) Schaarschmidt reported that NO.sub.2 gas was introduced into the mixture of benzene and aluminum chloride or ferric chloride to form a complex, followed by hydrolysis to obtain nitrobenzene. (refer to ibid)
(3) Paul Schorigin and A. Toptschien reported that benzene was reacted with nitrogen dioxide under the irradiation or no irradiation of ultraviolet ray in the presence of carbondioxide in such a manner that the nitration reaction was carried out in the molar ratio of benzene to N.sub.2 O.sub.4 and CO.sub.2 being 1 : 4 : 3.6 at the temperature of 25.degree. - 30.degree. C or 55.degree. - 60.degree. C in 2 hours, resulting in a yield of nitrobenzene about 30% based on benzene. That is to say, the conversion rate was about 40 - 50%, the selectivity rate was about 75 - 65%, and the recovery rate of benzene was about 60 - 50%. They said that the influence of ultraviolet ray irradiation on the reaction was not recognized. (refer to B. 67 1363 [1934]). And furthermore, almost the same description are found on page 236, FNT A. B. Topchiev, Izbrannye Trudy Nitrovania Izdatelstovo "Nauka", Moscow, 1965.
(4) Referring to the above Russian literature, on page 265, it was described that liquid N.sub.2 O.sub.4 was added into benzene in the presence of BF.sub.3 to produce nitrobenzene. The reaction may be summarized as follows. 0.5 mol N.sub.2 O.sub.4 reacted with 1 mol benzene in the presence of BF.sub.3 and obtained 22g nitrobenzene in a yield of 18% based on benzene. The reaction temperature rose to 55.degree. - 60.degree. C by adding N.sub.2 O.sub.4 drop by drop into benzene, because of exothermic reaction, and the reaction mixture was kept at that temperature during 1.5 - 2 hours.
(5) Furthermore, on page 266 of the same literature, the reaction of benzene with NO.sub.2 in the presence of catalyst at an elevated temperature of 310.degree. C was described. Nitrobenzene was obtained in the yield of 30.1% in the case of molar ratio of NO.sub.2 to benzene 2 : 1, while the yield reached to 83.6% at the same reaction temperature by increasing the molar ratio of NO.sub.2 to benzene till 7 : 1.
In addition, referring to Encyclopaedia of Chemical Technology edited by Kirk - Othmer Vol. 9 page 317, mononitro derivatives of aromatic hydrocarbon are prepared, using HNO.sub.3 or NO.sub.2 (equilibrium mixture of NO.sub.2 and N.sub.2 O.sub.4) in the presence of a catalyst at 130.degree. - 430.degree. C.
(6) On the same page of the above reference, nitration of vapor of benzene has been performed by gaseous nitrogen dioxide in a glow discharge in a Siemens type tube.
Among the products of the reaction were nitrobenzene, m-dinitrophenol and trinitrophenol.
(7) Referring to C.A. Vol. 73 1970 824746, .gamma.-radiation-induced nitration of benzene with liquid N.sub.2 O.sub.4 at the temperature of 20.degree. C has been described. The major product was nitrobenzene with isomers of dinitrobenzene.